Method for operating a dishwasher

ABSTRACT

A method for operating a dishwasher is provided. During a first phase, the dishwasher is operated with a first fluid quantity that is heated by a desorption process of a drying material. The first fluid quantity is increased to a second fluid quantity by adding a third fluid quantity that is stored in the drying material. During a second phase, the dishwasher is operated with the second fluid quantity. The first and second fluid quantities are circulated by a circulation pump during the first and second phases, respectively. The circulation pump is operated at a rotational speed that is higher during the second phase than during the first phase.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Divisional, under 35 U.S.C. §121, of U.S. application Ser. No. 13/058,542, filed Feb. 11, 2011, which is a U.S. national stage application under 35 U.S.C. §371 of PCT/EP2009/060232, filed Aug. 6, 2009, which designated the United States; this application also claims the priority, under 35 U.S.C. §119, to German Application No. 10 2008 043 551.1, filed Nov. 7, 2008 and to German Application No. 10 2008 039 888.8, filed Aug. 27, 2008.

BACKGROUND OF THE INVENTION

The invention relates to a method for operating a dishwasher, in particular a household dishwasher.

Dishwashers are known which run through wash programs comprising a plurality of program steps, such as prewash, wash, intermediate rinse, final rinse and drying of the items being washed for example. During some of these program steps, such as prewash or wash for example, fluid is applied to the items being washed to detach dirt, the fluid being heated by means of a heating means configured as a flow-through heater to enhance the cleaning action and detergent is added during a program step wash for example.

BRIEF SUMMARY OF THE INVENTION

The object of the invention is to improve the cleaning performance further.

The invention is based on a method for operating a dishwasher, in particular a household dishwasher, in which during at least a first phase operation takes place with a first predefined quantity of fluid and during a second phase operation takes place with a second predefined quantity of fluid, the first quantity of fluid being less than the second quantity of fluid.

According to the invention provision is made for a quantity of fluid stored in a fluid reservoir to be added to increase the first quantity of fluid to the value of the second quantity of fluid. In a program step with a washing action, such as the program step wash for example, this allows the spray pressure of the fluid coming out of the spray arms of the dishwasher to be increased by increasing the speed of a circulation pump, thereby improving cleaning performance without fluid, e.g. water, additionally having to be taken from a house-side water supply system. This conserves natural resources. It is possible here for fluid, such as water, for example fresh water or even used wash liquor, to be stored in an intermediate manner in the fluid reservoir in the time period between two uses of the dishwasher, in other words between two wash program runs, each consisting of a plurality of program steps, such as prewash, wash, intermediate rinse, final rinse and/or drying for example.

In one development provision is made for a drying means to be used as the fluid reservoir. This allows fluid to be stored in an intermediate manner and/or to be heated by waste heat and/or optionally also to be recycled, so that the overall water requirement can be reduced.

In one development provision is made for essentially a quantity of fluid of between 0.1 and 1 1, in particular between 0.2 and 0.5 1 to be added from the drying means. This means that a quantity of water stored in the drying means during a drying process can be recycled essentially in totality to improve the cleaning performance.

In one development provision is further made for a drying means suitable for exothermic drying to be used, in particular for drying cleaned items.

To this end in one development provision is made for a reversibly dehydratable drying means, in particular zeolite, of a sorption drying system to be used. This drying material features a high water absorption capacity and good reversible dehydratability.

In one development provision is further made for a quantity of fluid to be heated by a desorption process of the drying means during the first phase. This allows particularly energy-efficient cleaning with heated fluid, e.g. with water containing detergent.

In one development provision is further made for a quantity of fluid to be heated by a water heater during the second phase. This allows rapid further heating to higher temperatures, thereby improving the cleaning performance further.

In one development provision is made for a quantity of fluid to be circulated by means of a circulation pump during the first phase and the second phase, with the circulation pump being operated at a higher speed during the second phase than during the first phase. This allows the cleaning performance to be improved significantly, particularly during the second phase.

In one development provision is made for the circulation pump to be operated at least periodically in the true running state during the second phase. This allows particularly quiet operation, since in the true running state the circulation pump does not take in any air.

The object of the invention is further achieved by a dishwasher, in particular a household dishwasher, in particular with a sorption drying system, which at least during a first phase performs an operation with a first predefined quantity of fluid and during a second phase performs an operation with a second predefined quantity of fluid, the first quantity of fluid being less than the second quantity of fluid, with provision being made according to the invention for it to be possible for a stored quantity of fluid to be added to the first quantity of fluid from a drying means, to increase the first quantity of fluid to the value of the second quantity of fluid.

Other developments of the inventive dishwasher are set out in the subclaims.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention and its developments are described in more detail below with reference to drawings, in which:

FIG. 1 shows a schematic diagram of an exemplary embodiment of an inventive dishwasher with a sorption drying system,

FIG. 2 shows a schematic diagram of the temperature profile during a first exemplary embodiment of an inventive wash program run,

FIG. 3 shows a schematic diagram of the temperature profile of a further, second exemplary embodiment of an inventive wash program run, and

FIG. 4 shows a schematic diagram of the temperature profile of a further, third exemplary embodiment of an inventive wash program run.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS OF THE PRESENT INVENTION

Reference is made first to FIG. 1.

A dishwasher GS, configured in the present exemplary embodiment as a household dishwasher, has an interior IR serving as a washing container, which can be opened and closed for loading and unloading by means of a door (not shown) hinged to the dishwasher GS in a pivotable manner Racks GK for holding items to be washed are provided in the interior IR of the dishwasher GS, it being possible to pull said racks GK out of the interior IR of the dishwasher GS to facilitate loading and unloading.

To clean the items to be washed supported in the racks GK, means for applying fluid to the items to be washed configured as spray arms SA are provided in the interior IR of the dishwasher GS, it being possible for the fluid to be for example water mixed with detergents or rinse aid, in order thus to bring about a cleaning action or streak-free drying. The fluid flowing off the items being washed collects in a pump sump PS, which is disposed in the base region of the interior IR of the dishwasher GS.

The spray arms SA are connected in a fluid-conducting manner by way of a supply line ZL to a circulation pump UP, which is disposed along with other components of the dishwasher GS in a base assembly BO beneath the interior IR of the dishwasher GS. During operation, i.e. when the circulation pump UP is running, the circulation pump UP sucks up the fluid collected in the pump sump PS and conveys it through the supply line ZL to the spray arms SA. To heat the fluid circulated by operation of the circulation pump UP, the circulation pump has an integrated water heater WZ for heating the fluid. Alternatively a separate flow-through heater or another water heater can be provided in addition to the circulation pump UP. A drain pump LP is provided to empty the interior IR of the dishwasher GS, being likewise connected in a fluid-conducting manner to the pump sump PS and being able to be connected by way of a discharge line EL to a house-side waste water disposal network.

The dishwasher GS further features a sorption drying system, which can be used to dry cleaned items disposed in the racks GR at the end of a wash program run. To this end a sorption container SB is provided in the base assembly BO, being connected in an air-conducting manner to an inlet EI by way of an air channel LK, with a fan LT being provided to generate a forced throughflow. To convey the air sucked in through the inlet EI and conveyed into the sorption container by the fan LT back into the interior IR of the dishwasher GS, an outlet opening AU is provided in the base region of the interior IR of the dishwasher GS.

To bring about drying of cleaned items, the fan LT sucks in air from the interior IR of the dishwasher GS, conducts it through the sorption container SB and back through the outlet opening AU into the interior IR of the dishwasher GS. In order to dry the circulated air in this process, a drying means for performing exothermic drying is provided in the sorption container SB. This is a reversibly dehydratable drying material, e.g. zeolite, that absorbs water due to its hydroscopic nature, in which process thermal energy is simultaneously released. This released energy causes the circulated air to be heated, thereby raising the moisture absorption capacity of the circulated air. At the end of a drying process a quantity of fluid is stored in the drying material ZEO.

To restore the absorption capacity of the drying means ZEO for a new wash program run, an air heater HZ is provided, which is disposed in the sorption container SB in the present exemplary embodiment. It is however also possible to dispose an air heater outside the sorption container SB, e.g. in the air channel LK, to bring about heating of the air conveyed into the sorption container SB. An air flow generated using the fan LT is heated to drive out the quantity of fluid stored in the drying material ZEO, so that the drying material ZEO can be heated to temperatures at which the quantity of water stored in the drying material ZEO can be released again.

We will now look at FIGS. 2 to 4.

To wash and dry items to be washed, dishwashers GS run through wash programs that consist of a plurality of program steps that are run through one after the other. Such a program can consist of the program steps prewash V, wash R, intermediate rinse Z, final rinse K and drying T, it being possible also to omit individual program steps such as prewash V or intermediate rinse Z while it is also possible to run individual program steps a number of times, e.g. intermediate rinse Z. During the prewash V water with no detergent added for example is applied to the items to be washed, this taking place either with unheated water or with water heated using a heater. To this end water that has been stored in a water tank (not shown) can be used. Such a water tank can be connected in a thermally conducting manner to the environment of the dishwasher, so that fluid stored in an intermediate fashion in the water tank, e.g. water from a house-side supply system, can be heated to ambient temperature. In the washing step R the items to be washed are cleaned by the application of water containing detergents, i.e. detergent is added during the washing step. The fluid is also heated in order thus to enhance the cleaning action of the detergent. The washing step R here is made up of a heating phase P1, P2, in which the fluid in the dishwasher GS is heated by heating means, until a predefined maximum temperature is reached and a subsequent post-wash phase, during which the heating means are switched off and the slowly cooling fluid is circulated by means of the circulation pump UP. In the program step intermediate rinse Z fluid is applied to the items to be washed, to convey dirt residues out of the dishwasher GS. The next program step is the final rinse K in preparation for the drying program step T, in which water containing rinse aid is circulated by means of the circulation pump and applied to the now cleaned items by way of the spray arms SA. The program step drying T then follows, in which fluid is no longer applied to the items but operation of the fan LT causes an air flow circulating through the interior IR of the dishwasher GS and the sorption container SB to be generated. A full or at least partial fluid change can be effected between the individual program steps, in other words the dishwasher GS is emptied by means of the drain pump LP and the discharge line EL and refilled by a supply line (not shown) that establishes a connection to a house-side supply system.

With the wash program sequence according to FIG. 2 fluid is only heated in the program step wash R. Starting from a start temperature T0 during a first phase P1 the fluid circulated using the circulation pump UP is first heated by the air heater HZ in the sorption container SB to a maximum temperature T1, with the fan LT generating an air flow circulating through the interior IR of the dishwasher GS at the same time. The air heater HZ heats the drying material ZEO in the sorption container SB to temperatures at which the quantity of water stored in the drying material ZEO is driven out of the drying material ZEO and conveyed through the outlet opening AU in the interior IR of the dishwasher GS. This quantity of fluid is heated by the action of the air heater HZ and when mixed with the fluid already circulated by means of the circulation pump UP heats the overall quantity of fluid in the interior IR of the dishwasher GS.

The use of the air heater HZ during the program step wash R to heat up to the first temperature T1 ensures that the drying material ZEO can be reliably and completely desorbed by the circulation of relatively cold and dry air from the interior IR of the dishwasher GS. Instead of a rigid wash program sequence, in which a desorption process is performed in a first program segment, in which fluid is heated, in an alternative exemplary embodiment provision can also be made for evaluating parameters that influence the desorption process, to determine the time point for performing desorption. These parameters can be the air temperature and the water intake temperature. For example a desorption process can take place in a program step wash or final rinse or even during the program step prewash if expedient.

During desorption by means of the air heater HZ the outlet opening AU in the interior IR of the dishwasher GS is cooled, to ensure that the heat output of the air heater HZ does not cause excessive heating of the outlet opening HZ with overheating damage.

To this end during operation of the air heater HZ, i.e. during phase P1 for example, the circulation pump UP is operated in such a manner that fluid is conveyed by the circulation pump from the pump sump PS through the supply line to the spray arms SA. This causes the spray arms SA to rotate and the spraying of the outlet opening AU, in particular a cap covering the outlet opening AU, with fluid brings about cooling of the same.

In a next phase P2 of the program step wash R the water heater WZ heats the quantity of fluid from the first temperature T1 to the second temperature T2.

To enhance the cleaning action during the program step wash R provision is made to increase the spray pressure of the jets of water coming out of the spray arms SA by increasing the speed of the circulation pump UP. To this end during the program step wash R in the post-wash phase NA the quantity of fluid circulated by the circulation pump UP is increased by means of a top-up step, for example at time point t1 (see FIG. 2) and the speed of the circulation pump UP is then increased, e.g. continuously until the circulation pump again operates in true running conditions, in other words does not take in air bubbles during operation, which reduces the delivery rate of the circulation pump UP and causes unwanted noise to develop. It thus becomes possible to take account of the quantity of fluid that was stored in the drying material ZEO and is released during desorption when setting the quantity of top-up fluid, thereby reducing the overall water requirement whilst still improving cleaning performance.

A run-off phase AB is provided between the program step final rinse K and the program step drying T (see FIG. 2), during which fluid adhering to the washed items, i.e. water containing rinse aid, can run off the items in the dishwasher due to gravity and collect in the pump sump PS of the interior IR of the dishwasher GS. This reduces the quantity of fluid to be absorbed by the sorption drying system and thus the duration of the program step drying T.

Before this run-off phase AB, in other words at the end of the program step final rinse K, a pump-out process takes place, in which the fluid containing rinse aid is conveyed by means of the drain pump LP through the discharge line EL into a house-side waste water disposal system. The run-off phase AB follows, during which neither the circulation pump UP nor the drain pump LP, nor the fan LT nor any of the above-mentioned heaters HZ, WZ is in operation. After the end of this run-off phase AB the program step drying T starts by starting up the fan LT, so that an air flow circulating through the interior IR of the dishwasher and the sorption container SB is generated to dry the washed items in the racks GK. At the end of the program step drying T a further pump-out process takes place by means of the drain pump LP, by means of which a residual quantity of fluid is conveyed out of the dishwasher GS through the discharge line EL into a house-side waste water disposal system. Alternatively provision can also be made to perform a further pump-out process additionally or alternatively at the start of the program step drying T.

In the wash program according to FIGS. 3 and 4 fluid is heated in the first of the program steps, the program step prewash V. To this end the air heater HZ heats fluid from a start temperature T0 during a phase P1′ to a temperature T1′, in which, as described above, an air flow circulating through the interior IR of the dishwasher GS and the sorption container SB is generated by means of the fan LT. Once the temperature T1′ is reached, the air heater HZ is deactivated. At this time point the drying material ZEO is not yet completely desorbed, in other words a residual quantity of water is stored in the drying material ZEO. To drive this residual quantity of water out of the drying material ZEO and thus have a drying material ZEO with full water absorption capacity available again at the start of the program step drying T, in the next program step wash R the fluid is first heated by means of the air heater HZ to a temperature T1 and then by operation of the water heater to the temperature T2. In other words the desorption phase of the drying means ZEO in the sorption container SB is split into two and divided between two program steps, namely the program step prewash V and the program step wash R.

To enhance the cleaning action by further increasing the temperature, provision can be made for a further phase P3 (see FIG. 3), during which the fluid is further heated to a temperature T3 using the water heater WZ.

To improve the drying result at the end of the program step drying T, with the exemplary embodiments according to FIGS. 3 and 4 provision is made for the fluid to be heated during the final rinse step K. To this end during a phase P4 fluid, which is water or water containing rinse aid, is heated to a temperature T4 by means of the water heater WZ. Alternatively, instead of the water heater the air heater HZ can also be used, in order for example to complete a desorption that has not yet been fully performed during the program run. Additionally during a further phase P5 further heating of the fluid to a temperature T5 can take place, to improve drying using the sorption drying system. 

What is claimed is:
 1. A method for operating a dishwasher, the method comprising: during a first phase, operating the dishwasher with a first quantity of fluid and heating the first quantity of fluid by a desorption process of a drying material, wherein the first quantity of fluid is increased to a second quantity of fluid by adding a third quantity of fluid stored in the drying material; and during a second phase, operating the dishwasher with the second quantity of fluid; wherein the first quantity of fluid and the second quantity of fluid are circulated by a circulation pump during the first phase and the second phase, respectively; and wherein the circulation pump is operated at a rotational speed that is higher during the second phase than during the first phase.
 2. The method of claim 1, wherein the dishwasher is a household dishwasher.
 3. The method of claim 1, wherein the third quantity of fluid is between 0.11 and
 11. 4. The method of claim 3, wherein the third quantity of fluid is between 0.21 and 0.51.
 5. The method of claim 1, wherein the drying material is suitable for exothermic drying.
 6. The method of claim 5, wherein the drying material is suitable for drying cleaned items.
 7. The method of claim 5, wherein the drying material is a reversibly dehydratable drying material of a sorption drying system.
 8. The method of claim 7, wherein the reversibly dehydratable drying material is zeolite.
 9. The method of claim 1, wherein, during the second phase, at least one of the first, second, and third quantity of fluid is heated by a water heater.
 10. The method of claim 1, wherein, during the second phase, the circulation pump is operated at least periodically in a true running state.
 11. The method of claim 1, wherein, during a program step of a plurality of program steps with cleaning action, the third quantity of fluid stored in the drying material is added.
 12. The method of claim 11, wherein the program step is a wash program step with addition of detergent. 